Periodontal diseases are a major cause of tooth loss in adults. Recognition that microorganisms adhere to tissues such as teeth by specific structures (i.e., adhesins) suggest that regimes might be developed to inhibit adherence and colonization. The mechanisms by which periodontal disease-associated microorganisms attach to an accumulate on the teeth must be understood if periodontal diseases are to be controlled in this manner. The proposed project is a continuation of our studies on the mechanisms of adsorption by Actinomyces viscosus and A. naeslundii to teeth. One facet of the project is directed at characterizing the receptor binding region of the type 1 fimbriae which mediates attachment of A. viscosus to saliva-treated hydroxyapatite (SHA) in vitro. These studies will be approached be immunochemical analysis of isolated fragments of the immunoglobulins using SDS-PAGE gels and Western Blots. By combining the SDS-PAGE, HPLC, and Western Blot techniques with the receptor binding inhibition assay we plan to identify and isolate the receptor binding region type 1 fimbriae which mediates adsorption to SHA. Once this fragment has been identified monospecific and monoclonal antibodies will be prepared against it. We will then examine type 1 fimbriae from other Actinomyces strains to determine whether or not the receptor binding regions of these strains cross-react with that of strain T14V. Further we plan to use fimbrial-deficient mutant strains of strain T14V to determine if the proposed roles for type 1 and type 2 fimbriae in adherence and colonization established in vitro can be confirmed in vivo in humans and mice. Studies demonstrating that the teeth of mice immunized locally in the region of the salivary gland with a mixture of these fimbriae are resistant to colonization when challenged by that bacterial strain, will be expanded. These studies will determine the optimum dose and route of immunization, and whether type 1 or type 2 fimbriae singlely is as effective an immunogen as the mixture. The required role for fimbriae-specific salivary IgA in inhibiting adsorption or reducing colonization will also be evaluated. The principals established for reducing strain T14V colonization of teeth in mice by vaccination with fimbrial adhesins should by helpful in preventing colonization of other periodontopathogens by vaccination with other fimbrial adhesins.